Calcium is an important mineral that is used in many ways by the body. It strengthens your bones & teeth and also helps in muscle and nerve functions. Ionized calcium is an unbound calcium, not bound to any anions or proteins and circulates freely in the blood. Ionized calcium is vital in blood coagulation, nerve conduction, neuromuscular transmission and in muscle contraction. The ionized calcium levels are usually checked if the person is receiving blood transfusions, critically ill and on intravenous (IV) fluids, having had a major surgery, with abnormal levels of blood proteins such as albumin or immunoglobins in the blood.